Confidence Levels?

[magic_man]

I have a fairly good grasp of statistics and analysis, but I never took a statistics course. I know the 68-95-99 rule, but have a related question. How are these numbers calculated? From what I remember, they are the area under the curve between given standard deviations, right? In that case, is it the normal curve, and if so, what is the equation for this curve? I am specifically interested in an equation that will let me calculate how many standard deviations it takes to obtain a particular confidence level, say 92%. If I knew the equation of the curve, would I just do an integral .92 = int(equation) from -x to x, where x is the required number of standard deviations? Thanks for any help you guys can offer.

~Magic Man